Coaxial connector controlled characteristic impedance process

ABSTRACT

A coaxial connector for use with signals haVing components of an appreciable frequency is disclosed which includes a forward connector plug structure having a pair of spring arms shaped relative to an underlying dielectric insert and a center conductor to provide impedance matching. The connector includes a structure which facilitates termination of shielded and coaxial cable and a method is disclosed for controlling the deformation of material of the connector to provide impedance matching relative to a circuit path of use.

United States Patent 91 Reynolds 1 Jan.23, 1973 [54] COAXIAL CONNECTORCONTROLLED CHARACTERISTIC IMPEDANCE PROCESS Charles Edward Reynolds,Harrisburg, Pa.

Assignee: AMP Incorporated, Harrisburg, Pa.

Filed: July 2, 1970 Appl. No.: 30,052

Related U.S. Application Data Division of Ser. No. 698,092, Jan. 4,1968, Pat. No. 3,539,976.

lnventor:

[52] U.S. Cl ..29/593, 29/407, 29/630 A, 29/629, 324/57 Z, 29/203 D,29/60], 73/l F, 339/276 T, 339/220 T Int. Cl. ..H02g 15/00, HOlp 1 1/00Field of Search....29/593, 628, 630 A, 629, 407, 29/600, 601, 203 D, 203R; 324/57, 62, 64,

63, 60, 59; 73/] F; 339/276 T, 220 T [56] References Cited 2 ,525,45110/1950 Beggs ..324/60R F831;. "291593? 3,464,246 9/1969 Abromav ge etal. 29/593 UX 3,546,757 12/1970 l-loagenboom ..29/593 X 3 ,452,4299/1966 Liebscher ..29/592 Primary Examiner-Richard J. Herbst AssistantExaminer-Robert W. Church AttorneyCurtis, Morris and Safford, MarshallM. Holcombe, William Hintze, William J. Keating, Frederick W. Raring,John R. Hopkins, Adrian J. La Rue and Jay L. Seitchik [57] ABSTRACT Acoaxial connector for use with signals haVing components of anappreciable frequency is disclosed which includes a forward connectorplug structure having a pair of spring arms shaped relative to anunderlying dielectric insert and a center conductor to provide impedancematching. The connector includes a structure which facilitatestermination of shielded and coaxial cable and a method is disclosed forcontrolling the deformation of material ofthe connector to provideimpedance matching relative to a circuit path of use.

5 Claims, 12 Drawing Figures UIJTE TA Eslbeuialslsv We. 2%.. n.

SHEET 3 [IF 3 FEIT COAXIAL CONNECTOR CONTROLLED CHARACTERISTIC IMPEDANCEPROCESS This is a division of U.S. patent Application Ser. No. 698,092filed Jan. 4, 1968, now U.S. Pat. No. 3539976.

BACKGROUND OF THE INVENTION In applications calling for the terminationof coaxial leads which define circuit paths for signals of anappreciable frequency range such as several hundred l megacycles andabove, the prior art has generally turned to a precision screw machinedstructure. The general approach has been one of carefully defining theconductive surfaces of inner and outer conductors by rather heavy andsolidly continuous metallic bodies with spring members provided toassure matability and electrical continuity. Viewed in terms of actualmechanical and electrical requirements prior art structures represent anadequate but over-engineered solution to the problem of terminatingcoaxial cable. Viewed in terms of cost and overall reliability, the useof connectors having a relatively large number of small parts which mustbe assembled together in a cooperative relationship the prior artapproach represents a solution which is somewhat less than optimum fromthe standpoint of the end user.

As a problem related to the use of crimping techniques to terminatecoaxial cable, some considerable difficulties has been experienced inachieving a proper match of the impedance of the connector to that of agiven cable and circuit of use. In any connector structure which must becrimped to a coaxial cable there is always the possibility that indeforming portions of the connector to effect a mechanical andelectrical termination of the cable, the spacing between inner and outerconductive surfaces of the coaxial path represented by the connector andby portions of the cable within the connector may be so altered as toappreciably affect the characteristic impedance of such path. This is aparticular problem with so-called open barrel connectors wherein thereis no back-up ferrule against which the outer connector of a cable isdriven and supported under crimping forces applied to a surroundingferrule portion of a connector. With open barrel type connectors thereis also a problem caused by the presence of the seam which may or maynot be deformed to an extent to present a proper spacing of conductivesurface for impedance matching purposes.

SUMMARY OF THE INVENTION The present invention relates to a connectorfor coaxial and shielded cable which is capable of providing a matchedimpedance termination through a structure which is simple to manufactureand simple to terminate and which has fewer parts than heretoforerequired. The present invention also relates to a method of terminationof coaxial devices wherein deformationis controlled in accordance withan actual reading of impedance to assure a properly matched terminationof a connector to cable.

It is one object of the present invention to provide a coaxial connectordevice providing a matched impedance termination of coaxial and shieldedcable which can be quickly and easily accomplished. It is a furtherobject to provide a connector device for coaxial and shielded cablewherein impedance matching to a cable of use can be readily determinedduring termina- 0 and capable of providing a matched termination ofcable relying upon a mating receptacle structure to complete theconfiguration necessary for achieving a matched connection.

The foregoing objectives are attained through the present invention byan assembly of elements including a stamped and formed center contactmounted in an insulating and dielectric insert in turn mounted in astamped and formed outer conductive structure. The inner contact has anopen barrel portion which is aligned by the insert relative to the outerconductive portion so that a stripped cable may be laid into theconnector device with the outer conductive portion then being deformedinwardly to terminate both the inner and outer conductive portions of acable in a single stroke by dies simultaneously closed together. Thecenter contact includes a forward spring portion shaped with respect toa particular shaping of the dielectric insert and the forward portion ofthe outer conductor of the contact to provide impedance match when theconnector is inserted with a mating receptacle. As a separate aspect ofthe invention a method is 'disclosed relative to the foregoing connectordevice wherein as the connector is deformed inwardly to terminate theinner and outer conductive portions thereof to inner and outerconductors of the cable, the impedance presented by such deformation ismeasured with deformation being stopped when a proper impedance isachieved. The connector device of the invention may be utilized withcables of rather widely varying impedance characteristics by controllingsuch deformation. Alternatively, connector devices made to a loosetolerance can be applied in a manner providing a matched connection.

In the drawings:v

FIG. 1 is a perspective view showing a connector device in accordancewith a preferred embodiment of the invention just prior to receiving astripped coaxial and shielded cable;

FIG. 2 is an exploded view of the connector device of the inventionshown in FIG. 1;

FIG. 3 is a perspective view of the connector device as terminated to acable and prepared for use;

FIG. 4 is a side view showing portions of the connector of FIG. 1 and ofthe cable of FIG. 1 in section;

FIGS. 5, 6 and 7 are cross-sectional views of portions taken throughlines 5-5, 66 and 77 of FIG. 4;

FIG. 8 is a sectional view of a connector like that shown in FIG. 3 asmated with a receptacle; I

FIGS. 9 and 10 are cross-sectional views taken through lines 9-9 and10-10 of FIG. 8;

FIG. 11 is a perspective view illustrating the method aspect of theinvention in one embodiment wherein deformation of a connector deviceto-terminate it to a cable is monitored in terms of impedancecharacteristics; and

FIG. 12 is a schematic view illustrating the invention method in analternative embodiment.

Referring now to FIG. 1, a coaxial and shielded cable is revealed asincluding a center conductor 12 which is surrounded by a dielectricsheath. 14 and an outer conductor in the form of braid 16. The braid 16is shown folded back on the cable over an outer protective sheath 18. Itis contemplated that cable may be prepared in this fashion as shown inFIG. 1 or alternatively, in a similar manner but without folding thebraid back; merely exposing a length of the braid by stripping off theouter protective sheath 18 so that a similar portion of the braid islaid bare. Cable of this type is widely used to interconnect circuitpaths where there is a requirement for shielding of signals carried bythe center conductor 12 or limiting radiation from the conductor 12 ofsignals carried thereby to adjacent circuit paths. Cable of this type isalso utilized to transmit signals having frequency components resultingin transfer of energy at least in part through the dielectric medium 14between the conductive surfaces 12 and 16. Cable of the generalconfiguration of 10 may be made to have a specific characteristicimpedance such as 50 ohms or, with only a change in the inner conductorand the dielectric material of the sheath 14, to have the characteristicimpedance of 75 ohms or some other value. From external appearance theonly difference in the cable may appear as a reduction in diameter ofthe center conductor 12. Cable of the general configuration of 10 may bemade to a very close tolerance to provide a characteristic impedancevarying no more than t l percent or it may be made to a looser toleranceto provide variation in characteristic impedance of i 10 percent or thelike. The choice between precision cable or loosely toleranced cable isdetermined by the requirements of the circuit of use and by the costpermitted in a given application.

In FIG. 8 to the left of the view is a receptacle R including a tubularouter conductor 0C and an inner conductor IC in the form of a pinmember. In accordance with a widely accepted practice, the receptacle Ris made to standard specification with respect to the inner diameter ofOC and the outer diameter of IC. Considering air as the dielectricmedium therebetween, R provides a fixed and standard characteristicimpedance such as '50 or 75 ohms. The receptacle may be mounted on orproximate to a circuit of use with characteristic impedanceconsideration taken into account by the configuration of conductivepaths therein or thereto. The general problem to which the presentinvention relates is one of providing a mechanical and electricaltermination or connection extending between the cable 10 and thereceptacle R. There is the mechanical consideration of physicallyjoining the connector to the cable in a manner so that electricalcontinuity of inner and outer conductive paths will be maintained in aconstant and stable manner throughout the life of the connection formed.There is the related consideration of providing a signal transmissionpath which is sufficiently matched to the characteristic impedance ofthe receptacle and of the cable to preclude the connector device fromoperating as a source of reflections or in causing signal degradation orsignal loss with respect to signals transmitted to or from thereceptacle between the circuits connected thereto and the cable of use.

Referring again to FIG. 1, a connector device embodying aspects of theinvention and illustrating the invention is shown to be comprised of anassembly of three elements including an outer conductive shell 22, adielectric andinsulating insert 24 and a center contact member 26. Thearrangement of elements is such that a stripped and prepared cable maybelaid into the device rather than axially inserted. This permits aninitial installation of the prepared cable while minimizing alignmentproblems and the opportunity for displaced strands of 12 or 16accidentally coming into engagement with conductive portions other thanthose desired.

The outer conductive shell 22 shown in FIGS. 1-3 is comprised of aone-piece stamping of sheet metal such as brass, the forward contactportion, a center portion and a rear terminating portion. The forwardportion is, in FIG. 1, formed into a circular configuration 22a which isslightly less than the inner diameter of the receptacle R into which thedevice is to be plugged. The portion 22a also serves to look theassembly of the center contact member 26 and the insert 24 within shell22. Extending from 220 and approximately l apart are spring arms shownas 22b which, in a relaxed state, are bowed outwardly as indicated inFIG. 1. The spring arm 22b join the sidewalls of the center portion 220at a point thereon so as not to be appreciably displaced upondeformation of portion 22c from the configuration shown in FIGS. 1 and 2to the configuration shown in FIG. 3. The bow of spring arms 22b is madeto be sufficient to provide a spring action notwithstanding deformationof the portion 22c inwardly. Portion 220 includes a series of groovesshown as 22d on the inner surface of the portion which operate to gripthe material of the insert 24 during closure of the portion and tend tostabilize displacement of 24 against axial flow under the compression ofthe crimp which closes 22c. As can be discerned from FIG. 6, theprecrimped configuration of portion 220 is generally U-shaped with theends turning in to an extent to prevent the insert 24 from beingdisplaced even slightly in a radial sense with respect to the shell.

Joining portion 220 and extending rearwardly is a portion 22c whichcontains a series of relatively sharp grooves therewith shown as 22f.FIG. 4 shows the grooves 22f in greater detail. The grooves 22f servethe bite into the outer conductor 16 of the cable upon deformation of22a from the configuration shown in FIGS. 1 and 7 to the configurationshown in FIGS. 8 and 10. The grooves also operate to better grip thecable mechanically against pullout.

The dielectric insert 24 includes a central bore 24a which is roughlyD-shaped to admit the insertion of thecenter contact member 26 from thefront of the insert. The forward portion of the insert has an outsidecircular configuration as indicated from FIG. 2. Adjacent the forwardportion of 24 are two projections shown as 24b, which extend along thelength of the insert in the manner depicted in FIG. 2. These projectionsdefine an outside surface slightly greater than the diameter of theportion 22a, so as to engage the walls of R upon insertion of the devicewithin the receptacle. The portions 22!: also serve to hold the insertin position within the shell prior to deformation; the forward portionsengaging 22a and the rearward portions engaging the lower forwardsurface of 220 in the manner indicated in FIGS. 1 and 4. The portions22b are controlled in width to provide a surface of engagementstabilizing the device as terminated to a cable and inserted within Rwith the width of these portions being held to a minimum to accomplishthis purpose for impedance matching considerations. In other words, theportions 22!; are held to a width wherein a substantial portion of thedielectric medium surrounding the center contact is comprised of airrather than dielectric material. As shown in FIG. 2 the rear portion of24, shown as 240 is generally U-shaped to provide access of the cablecenter conductor to the center contact when the center contact is fittedwithin the insert. FIG. 6 depicts the cross-sectional configuration of24c and shows the beveling of the upper surfaces and the generalthickening of the structure for the upper portion thereof which has beenfound to result in a better control of the deformation of the centercontact structure which is made through the dielectric material inaccordance with the invention device.

The center contact 26 includes a forward circular portion 26a of a sizeto receive in sliding engagement the inner contact member IC of R asshown in FIG. 8. Adjacent 26a and as an integral extension are aplurality of spring arms shown as 26b which have an inward bow in arelaxed configuration to provide a spring loaded wipe of the innercontact of R. The spring arm 26b are tapered toward the center tocontrol insertion force and to minimize the conductive surface of 26 inthe spring region. The rear of 26 shown as 26c is open to receive thecenter conductor 12 of the cable inserted transverse to the length of26. The portion 260 has a corrugated surface which has been found toprovide an improved mechanical engagement with the center contact member12 and thereby to provide a low-re- "sistance stable interface with theconductive surface of the center conductor 12. As an additional pointthe serrations serve to lock the center contact member followingcrimping against axial displacement forwardly or rearwardly of thedevice. The center contact 26 further includes small flange 26d struckout at one point from the bottom thereof which serves to position 26 in24.

In assembly of the device, the center contact 26 is loaded from thefront of 24 and pushed back along the bore thereof until it is theposition shown in FIG. 4. At this time the outer shell 22 is in theconfiguration shown in FIG. 2 and the insert is positioned therein withthe lower projection 24b engaging the lower forward edge of 22c as shownin FIG. 4. Next, the forward portion 22a is deformed about the insert inthe manner indicated in FIG. 1 or in FIGS. 4 and 5 to lock the assemblyof elements together for use.

In use the connector devices are made to receive cable prepared like thecable shown in FIG. 1 or prepared without folding the cable back butexposing a portion of the braid 16 followed by a crimping anddeformation of the portions 220 and 22e into the configuration shown inFIGS. 9 and 10. As can be observed from FIG. 10, the conductive surfacesof 22 and 26 are maintained generally concentric. As can be observedfrom FIG. 9, at least in one embodiment, the cross-sectionalconfiguration of portion 22c is not quite concentric being slightly ovalor oblong. This configuration leaves opposing outside edges of theforward portion of 220 at a greater radius than the radius of the boreof R and this portion engages the end of R upon insertion into R to actas a stop limiting rather precisely the axial position of the devicerelative to R. From FIG. 8' it will be apparent that cable is laid intothe connector so as to leave a substantial space between the end of thebraid and the rear end of the insert and center contact member 26. Thisserves to preclude accidental shorting of the outer conductive path tothe inner conductive path.

In an application calling for a termination to a receptacle R of astandard size for 50 ohm impedance use, a connector having a solidlyformed outer-shell in the forward portion including a spring member wasfound to provide a mismatch which was unacceptable. In the standardexpression for characteristic impedance Z, 138/ ,l' log b/A, theeffective dielectric constant e for a solid dielectric insert and theinner diameter b of the outer conductive path of the connector were toohigh. The connector shown in this application matches impedance byproviding an effective spacing between inner and outer conductive paths(adjusting a and b) considering the dielectric material or medium(decreasing e) between conductive surfaces formed of the composite ofair and the material of the dielectric insert 24. The effectivecharacteristic impedance in the region of the spring configuration ofthe center contact member and the spring configuration of the outershell takes into account the conductive surfaces of 0C and the innerconductive surfaces of DC, as defining in part the conductive surfacesseen by energy transferred through the connection formed by 20 and R.The selective removal of conductive materialand of dielectric materialand the arrangement thereof has been found to offer a solution to theproblem of providing a spring type coaxial connector mateable with astandard receptacle which is far simpler than devices heretofore known.

Turning now to a further aspect of the invention, FIG. 11 depicts thetermination of a connector device like 20 through the use of a hand toolshown as T containing dies driven to effect the deformation heretoforedescribed of portions of the device to terminate it to a cable 10. Thetool contains a fixed die D1 and a movable die D2 which are driventogether to crimp the portions 22c and 22e. In accordance with thisaspect of the invention a length of cable 10 is laid into the terminaldevice which is then positioned within the tool. A further connectorshown as C which includes a forward receptacle R is then fitted on theforward portion of the connector device to be terminated. Theconnector'C is connected by a coaxial lead L to an impedance bridge 30for measuring impedance. The bridge 30 includes an output 32 which isterminated to the inner and outer conductors of the cable 10 as by somesuitable means shown as alligator clips 34. The bridge includes on theface thereof a scale in ohms and an indicator. In accordance with thisaspect of the invention as the dies D1 and D2 are closed the signalinjected into 10 is returned to 30 through the inner and outerconductive portions of the cable and of the terminal. As continuity ismade with the conductive portions of the cable and the device, theindicator will begin to drop from some high impedance level (opencircuit, infinity) down toward a lower level. For example, 'theindicator will move from full scale down toward 50 ohms. When theindicator reaches 50 ohms further deformation of the device onto thecable is stopped with the terminated be achieved by deforming the crimpportions until the indicator reads somewhere a little less than 50 ohmswith release of the dies resulting inthe indicator returning toprecisely 50 ohms. An impedance bridge of the type manufactured byHewlett Packard Company as a VHF Model 803A is commercially availablefor use with the foregoing method.

FIG. 12 shows an alternative set-up wherein the method of the inventionmay be employed without connecting the free end of cable 10. inaccordance with the showing in FIG. 12 a time domain reflectometer shownas TDR is made to have an output lead L connected to a connector C intowhich the device to be terminated is plugged. The connector device isshown as 20. The cable is laid into the terminal device and deformationfollows by closure of dies D1 and D2 with the impedance level beingobserved on the TDR and deformation continuing until the appropriateimpedance level is reached. The approach shown in FIG. 12 utilizesstandard apparatus which is commercially available. With lowerfrequencies care must be taken to make L long enough so that the site ofthe lumped impedance represented by the termination of to 10 is not tooclose to the TDR; i.e. so that L is longer than or A wavelength of thelowest frequency employed. A Hewlett Packard Company Model HPMISA TimeDomain Reflectometer is commercially available for use with theforegoing method.

The foregoing methods are visualized as having numerous applications forexperimentation and for production. As a most important aspect of themethod as related to the type of device disclosed, the elements may bemanufactured with relatively loose tolerances to reduce the cost thereofand to facilitate assembly with the functional performance thereof beingassured by controlling the deformation of portions of the elements toyield the properimpedance. Variations in tolerances or construction ofcable can also be accommodated.

In a typical use for a given quantity of connector devices and a givenquantity of certain types of cable the application tooling employed, beit hand tool, as depicted or what is more likely, a bench mounted pressor the like, the first connector device to be terminated on a given workshift can'be installed in the manner shown in FIGS. 11 and 12. Usingeither circuit a crimp may be made to achieve a desired impedance withthe dies of the application tooling being adjusted accordingly toprovide the precise control of deformation desired. After the dies havebeen set connector devices may be terminated to cables with a betterassurance that the desired impedance will be achieved. Alternatively, itmay be that in certain applications each connector device willbe-measured in accordance with a circuit arrangement shown in FIGS. 11or"l2 or it may be that the method can be practiced by measuring onlyevery tenth or every hundredth termination.

In an actual embodiment of the invention device for use with ohm cablehaving a solid silver flash copper center conductor surrounded by sheathof Teflon material and a braided outer conductor. The outer shell wasmade of sheet stock brass approximately 0.010 of an inch in thickness.The .insert was of polyethylene molded to the configuration shown andthe center contact was of beryllium copper stamped and formed to theconfiguration shown out of 0.004 of an inch thick stock. The forwardportion of the device of 22a was of an outer diameter of 0.100 of aninch. The spring arms were approximately 0.035 of an inch in width. Thedielectric insert measured approximately 0.030 of an inch in the widestdimension across the projections 24a and approximately 0.080 of an inchin outer diameter in the cylindrical portion apart from the projections24a. The device was used with a receptacle having an inner diameter of0C equal to approximately 0.105 of an inch with an inner'contact member[C of an outer diameter of approximately 0.040 of an inch. The devicewas found to operate satisfactorily in a 50'ohm circuit.

Having now disclosed the invention in terms intended to enable apreferred practice thereof, the following clainis are set forth todefine what is asserted to be inventive.

What is claimed is:

1. In a method of terminating coaxial or shielded cable of the typehaving an inner conductor surrounded by a dielectric and an outerconductor and wherein such cable has a given characteristic impedance,which comprises the steps of:

a. placing'a stripped and prepared coaxial cable into a stamped andformed U-shaped connector;

b. commencing to connect said connector to said coaxial cable bycrimping said connector onto. said cable;

c. measuring the impedance of said connection during said crimping; and

d. stopping said crimping when the impedance of said co'nnection matchesthe given characteristic impedance of said coaxial cable.

2. The method of claim 1 including the step of injecting a signalthrough the connector in engagement with said cable and measuring theeffect upon said signal in terms of the impedance of the circuit formedby said connector and said cable during deformation of said connectorportion.

3. The method of claim 1 wherein the step of measuring the impedance ofsaid connection includes the step of injecting a signal into saidconnector device and the cable to which it is being terminated andmeasuring the signal components reflected by said termination todetermine impedance.

4. The method of terminating coaxial cable to a connector whichcomprises the steps of:

a. supplying a stamped and formed electrical connectgr lof the typehaving a U-shaped outer conductive s e l; 1 b. laying a coaxial cable ofa given impedance and of the typehaving an inner conductor surrounded bya dielectric and an outer conductor, into said electrical connector;

c. crimping said electrical connector onto said coaxial cable causing aconnection thereinbetween; d. measuring the impedance of saidconnection; and

e. continuing said crimping until the impedance of said connectionmatches that of said coaxial cable.

5. A method of connecting an electrical connector onto a coaxial cableof a given impedance and having an outer conductor, an inner conductorand a dielectric thereinbetween, which comprises the steps of:

a. providing an electrical connector of the type having a U-shaped outerconductive shell, a center contact member having a opened U-shaped rearportion and a dielectric member positioned between said outer shell andsaid center member;

b. preparing the coaxial cable whereby a end of the inner conductor isuncovered and a portion of the outer conductor is exposed;

c. positioning said inner conductor of said coaxial cable into saidU-shaped rear portion of said center contact member of said connector sothat said exposed outer conductor of said coaxial cable is positionedinto a portion of said U-shaped outer shell of said connector;

. causing a connection between said connector and stopping said crimpingwhen the impedance of the connection matches the impedance of saidcoaxial cable.

1. In a method of terminating coaxial or shielded cable of the typehaving an inner conductor surrounded by a dielectric and an outerconductor and wherein such cable has a given characteristic impedance,which comprises the steps of: a. placing a stripped and prepared coaxialcable into a stamped and formed U-shaped connector; b. commencing toconnect said connector to said coaxial cable by crimping said connectoronto said cable; c. measuring the impedance of said connection duringsaid crimping; and d. stopping said crimping when the impedance of saidconnection matches the given characteristic impedance of said coaxialcable.
 2. The method of claim 1 including the step of injecting a signalthrough the connector in engagement with said cable and measuring theeffect upon said signal in terms of the impedance of the circuit formedby said connector and said cable during deforMation of said connectorportion.
 3. The method of claim 1 wherein the step of measuring theimpedance of said connection includes the step of injecting a signalinto said connector device and the cable to which it is being terminatedand measuring the signal components reflected by said termination todetermine impedance.
 4. The method of terminating coaxial cable to aconnector which comprises the steps of: a. supplying a stamped andformed electrical connector of the type having a U-shaped outerconductive shell; b. laying a coaxial cable of a given impedance and ofthe type having an inner conductor surrounded by a dielectric and anouter conductor, into said electrical connector; c. crimping saidelectrical connector onto said coaxial cable causing a connectionthereinbetween; d. measuring the impedance of said connection; and e.continuing said crimping until the impedance of said connection matchesthat of said coaxial cable.
 5. A method of connecting an electricalconnector onto a coaxial cable of a given impedance and having an outerconductor, an inner conductor and a dielectric thereinbetween, whichcomprises the steps of: a. providing an electrical connector of the typehaving a U-shaped outer conductive shell, a center contact member havinga opened U-shaped rear portion and a dielectric member positionedbetween said outer shell and said center member; b. preparing thecoaxial cable whereby a end of the inner conductor is uncovered and aportion of the outer conductor is exposed; c. positioning said innerconductor of said coaxial cable into said U-shaped rear portion of saidcenter contact member of said connector so that said exposed outerconductor of said coaxial cable is positioned into a portion of saidU-shaped outer shell of said connector; d. causing a connection betweensaid connector and said coaxial cable by crimping said U-shaped rearportion of said center contact member over said inner conductor and bycrimping a portion of said U-shaped outer conductive shell over saidexposed outer conductor and simultaneously measuring the impedance ofsaid connection; and e. stopping said crimping when the impedance of theconnection matches the impedance of said coaxial cable.